The present invention relates to an engine igniting coil device.
Recently, there has been developed such an engine igniting coil device which comprises one coil case wherein a plurality of coil units selected in accordance with a quantity of engine cylinders are arranged with no use of a distributor and unitarily formed by potting with insulating material such as epoxy resin and the like.
In such an engine igniting coil device of prior art, as shown in FIG. 15, coil units 1, 2, 3 arranged in a coil case 5' are all embedded with resin 17 injected therearound. However, this method requires a large amount of resin 37 for potting the coils in the case 5' resulting in increase of the device's weight. Furthermore, since each of the coil units 1,2 and 3 has an exposed core portion 40 of closed magnetic circuit type which extrudes from a coil portion 41 wound thereon, the units may be potted with unevenly thick layers of resin in the case. Therefore, such a disadvantage is caused that thermal expansion and shrinkage of the core units 1,2 and 3 potted in the case create a stress concentrated on a thinner portion of resin layer whereat cracks may be easily formed.
In the prior art, a case 5' has a relatively large inner space in which a plurality of coil units 1, 2 and 3 are mounted and resin 37 is then poured to fill up the rest space portion thereof. An engine igniting coil device thus manufactured may not free from the possibility that its cured resin portion of the case 5' expands and shrinks by affection of thermal shock produced by change of surrounding temperature and may suffer cracking when a relatively large thermal distortion is applied thereon.
Furthermore, in case when a noise killer condenser is also potted in the ignition coil case for the purpose of preventing the noise from affecting audio-visual devices mounted in a vehicle for which the ignition coil device is used, it may be easily damaged under the thermal stress applied thereon through the surrounding layer of resin.